Class: Sequel::Model::Associations::EagerGraphLoader

Inherits:
Object
  • Object
show all
Defined in:
lib/sequel/model/associations.rb

Overview

This class is the internal implementation of eager_graph. It is responsible for taking an array of plain hashes and returning an array of model objects with all eager_graphed associations already set in the association cache.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(dataset) ⇒ EagerGraphLoader

Initialize all of the data structures used during loading.


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# File 'lib/sequel/model/associations.rb', line 3727

def initialize(dataset)
  opts = dataset.opts
  eager_graph = opts[:eager_graph]
  @master =  eager_graph[:master]
  requirements = eager_graph[:requirements]
  reflection_map = @reflection_map = eager_graph[:reflections]
  reciprocal_map = @reciprocal_map = eager_graph[:reciprocals]
  limit_map = @limit_map = eager_graph[:limits]
  @unique = eager_graph[:cartesian_product_number] > 1
      
  alias_map = @alias_map = {}
  type_map = @type_map = {}
  after_load_map = @after_load_map = {}
  reflection_map.each do |k, v|
    alias_map[k] = v[:name]
    after_load_map[k] = v[:after_load] if v[:after_load]
    type_map[k] = if v.returns_array?
      true
    elsif (limit_and_offset = limit_map[k]) && !limit_and_offset.last.nil?
      :offset
    end
  end
  after_load_map.freeze
  alias_map.freeze
  type_map.freeze

  # Make dependency map hash out of requirements array for each association.
  # This builds a tree of dependencies that will be used for recursion
  # to ensure that all parts of the object graph are loaded into the
  # appropriate subordinate association.
  dependency_map = @dependency_map = {}
  # Sort the associations by requirements length, so that
  # requirements are added to the dependency hash before their
  # dependencies.
  requirements.sort_by{|a| a[1].length}.each do |ta, deps|
    if deps.empty?
      dependency_map[ta] = {}
    else
      deps = deps.dup
      hash = dependency_map[deps.shift]
      deps.each do |dep|
        hash = hash[dep]
      end
      hash[ta] = {}
    end
  end
  freezer = lambda do |h|
    h.freeze
    h.each_value(&freezer)
  end
  freezer.call(dependency_map)
      
  datasets = opts[:graph][:table_aliases].to_a.reject{|ta,ds| ds.nil?}
  column_aliases = opts[:graph][:column_aliases]
  primary_keys = {}
  column_maps = {}
  models = {}
  row_procs = {}
  datasets.each do |ta, ds|
    models[ta] = ds.model
    primary_keys[ta] = []
    column_maps[ta] = {}
    row_procs[ta] = ds.row_proc
  end
  column_aliases.each do |col_alias, tc|
    ta, column = tc
    column_maps[ta][col_alias] = column
  end
  column_maps.each do |ta, h|
    pk = models[ta].primary_key
    if pk.is_a?(Array)
      primary_keys[ta] = []
      h.select{|ca, c| primary_keys[ta] << ca if pk.include?(c)}
    else
      h.select{|ca, c| primary_keys[ta] = ca if pk == c}
    end
  end
  @column_maps = column_maps.freeze
  @primary_keys = primary_keys.freeze
  @row_procs = row_procs.freeze

  # For performance, create two special maps for the master table,
  # so you can skip a hash lookup.
  @master_column_map = column_maps[master]
  @master_primary_keys = primary_keys[master]

  # Add a special hash mapping table alias symbols to 5 element arrays that just
  # contain the data in other data structures for that table alias.  This is
  # used for performance, to get all values in one hash lookup instead of
  # separate hash lookups for each data structure.
  ta_map = {}
  alias_map.each_key do |ta|
    ta_map[ta] = [row_procs[ta], alias_map[ta], type_map[ta], reciprocal_map[ta]].freeze
  end
  @ta_map = ta_map.freeze
  freeze
end

Instance Attribute Details

#after_load_mapObject (readonly)

Hash with table alias symbol keys and after_load hook values


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# File 'lib/sequel/model/associations.rb', line 3685

def after_load_map
  @after_load_map
end

#alias_mapObject (readonly)

Hash with table alias symbol keys and association name values


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# File 'lib/sequel/model/associations.rb', line 3688

def alias_map
  @alias_map
end

#column_mapsObject (readonly)

Hash with table alias symbol keys and subhash values mapping column_alias symbols to the symbol of the real name of the column


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# File 'lib/sequel/model/associations.rb', line 3692

def column_maps
  @column_maps
end

#dependency_mapObject (readonly)

Recursive hash with table alias symbol keys mapping to hashes with dependent table alias symbol keys.


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# File 'lib/sequel/model/associations.rb', line 3695

def dependency_map
  @dependency_map
end

#limit_mapObject (readonly)

Hash with table alias symbol keys and [limit, offset] values


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# File 'lib/sequel/model/associations.rb', line 3698

def limit_map
  @limit_map
end

#masterObject (readonly)

The table alias symbol for the primary model


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# File 'lib/sequel/model/associations.rb', line 3701

def master
  @master
end

#primary_keysObject (readonly)

Hash with table alias symbol keys and primary key symbol values (or arrays of primary key symbols for composite key tables)


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# File 'lib/sequel/model/associations.rb', line 3705

def primary_keys
  @primary_keys
end

#reciprocal_mapObject (readonly)

Hash with table alias symbol keys and reciprocal association symbol values, used for setting reciprocals for one_to_many associations.


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# File 'lib/sequel/model/associations.rb', line 3709

def reciprocal_map
  @reciprocal_map
end

#records_mapObject (readonly)

Hash with table alias symbol keys and subhash values mapping primary key symbols (or array of symbols) to model instances. Used so that only a single model instance is created for each object.


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# File 'lib/sequel/model/associations.rb', line 3713

def records_map
  @records_map
end

#reflection_mapObject (readonly)

Hash with table alias symbol keys and AssociationReflection values


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# File 'lib/sequel/model/associations.rb', line 3716

def reflection_map
  @reflection_map
end

#row_procsObject (readonly)

Hash with table alias symbol keys and callable values used to create model instances


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# File 'lib/sequel/model/associations.rb', line 3719

def row_procs
  @row_procs
end

#type_mapObject (readonly)

Hash with table alias symbol keys and true/false values, where true means the association represented by the table alias uses an array of values instead of a single value (i.e. true => *_many, false => *_to_one).


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# File 'lib/sequel/model/associations.rb', line 3724

def type_map
  @type_map
end

Instance Method Details

#load(hashes) ⇒ Object

Return an array of primary model instances with the associations cache prepopulated for all model objects (both primary and associated).


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# File 'lib/sequel/model/associations.rb', line 3827

def load(hashes)
  # This mapping is used to make sure that duplicate entries in the
  # result set are mapped to a single record.  For example, using a
  # single one_to_many association with 10 associated records,
  # the main object column values appear in the object graph 10 times.
  # We map by primary key, if available, or by the object's entire values,
  # if not. The mapping must be per table, so create sub maps for each table
  # alias.
  @records_map = records_map = {}
  alias_map.keys.each{|ta| records_map[ta] = {}}

  master = master()
      
  # Assign to local variables for speed increase
  rp = row_procs[master]
  rm = records_map[master] = {}
  dm = dependency_map

  records_map.freeze

  # This will hold the final record set that we will be replacing the object graph with.
  records = []

  hashes.each do |h|
    unless key = master_pk(h)
      key = hkey(master_hfor(h))
    end
    unless primary_record = rm[key]
      primary_record = rm[key] = rp.call(master_hfor(h))
      # Only add it to the list of records to return if it is a new record
      records.push(primary_record)
    end
    # Build all associations for the current object and it's dependencies
    _load(dm, primary_record, h)
  end
      
  # Remove duplicate records from all associations if this graph could possibly be a cartesian product
  # Run after_load procs if there are any
  post_process(records, dm) if @unique || !after_load_map.empty? || !limit_map.empty?

  records_map.each_value(&:freeze)
  freeze

  records
end